1. Field of the Invention
The invention relates to a method for controlling an electric motor of a vehicle pump, a program element, a delivery device of a vehicle, and a vehicle.
2. Description of the Prior Art
Typical fuel pumps for diesel fuel can have a pumping unit that according to the displacement principle. An example of this can be the gerotor pump or gear ring pump. Screw and roller vane pumping units can also be used as fuel pumps. During the operation of fuel pumps, different operating states can occur depending on the pressure and the viscosity of the medium to be delivered. Since pumping units which work by the displacement principle can typically have a high hydraulic-mechanical rigidity, a change in the viscosity or the pressure of the delivered medium can have a direct impact on the necessary torque needed to drive the pump.
At present, electrically commutated motors can be used in fuel pumps. These are synchronous machines that may have fluctuations in the available output torque over the course of the angle of rotation of the rotor, owing to their design. Moreover, typical displacement pumps can have fluctuating load torques over the course of the angle of rotation. A brief exceeding of the available output torque of the electric motor, due to the load torque of the pump, can result in a loss of synchronization between rotor and driving field. This can result in a drop in speed and a loss of control of the electronics over the electric motor with subsequent pump standstill.
Moreover, other disruptive effects can occur in pumps with gerotor mechanism when they are operated at low speed. Due to manufacturing tolerances, there may also be fluctuations in the required torque over several revolutions of the gerotor. These periodic fluctuations in load torque together with the fluctuations in the output torque of the electric motor due to rotor angle can result in both fluctuations in the true running of the pump over several of its revolutions and fluctuations over partial revolutions. Typically, the electronics of the pump can work as a speed regulator of the fuel pump according to a speed setpoint signal from the engine controls. At low speed of the pump or the electric motor and at certain pressures in the pumping unit, this mechanically inducted behavior can even lead to a loss of control of the electronics over the pump and thus to a pump standstill.